The use of mobile phones has become more and more popular recently for the provision of fast and convenient communication. The power source of the mobile phone generally comes from a rechargeable battery, therefore charging efficiency and the durability of the battery are important issues. The conventional charging device generally conveys electrical power to the battery of the mobile phone through metal contact thereof and the mating metal contact of the battery to be charged. More particularly, the metal contacts are generally formed to have specific number and shape to delivers electrical energy efficiently between the battery and charging device.
However, the metal contact of the charging device and the mating metal contact may have poor contact therebetween if the battery is not precisely aligned with the charging device. The charging efficiency is degraded and the charging time is prolonged due to the poor contact between those metal contacts.
The transmission of electrical energy by coil induction has been adopted in the application of electric tooth-brush. More particularly, the tooth-brush contains a barrel-shaped iron core to receive electrical energy induced from a cylindrical iron core energized by a power source. However, the alignment tolerance of above-mentioned induction-type energy transmission method is not sufficient for the application of mobile phone.
It is an object of the present invention to provide a charging device for mobile phone which uses coil induction to convey electrical energy, thus increasing the alignment tolerance between battery and charging device, and enhancing the charging efficiency.
To achieve the above objects, the present invention provides a charging device which has an induced-type power supply device and a charging stage. The induced-type power supply device comprises an induced iron core, a secondary coil around the surface of the iron core, an induced-type power transmission device and a sensor connected to the iron core. The charging stage comprises a primary iron core of ringer-shape, a primary coil around the surface of the primary iron core, a power source and a controller connected to the coil. When the battery of the mobile phone is to be charged, the power supply generates an intense magnetic field through sending current to the primary coil around the primary iron core. The generated magnetic field induces electric current on the secondary coil around the induced iron core, which can charge the battery through the induced-type power transmission device and the sensor.
The above-mentioned sensor is functioned to detect the charging state of the battery, such as the charging voltage, the charging current and the remaining charge. The sensor will send a warning signal to the controller to reduce or turn off charging voltage in case that the charging voltage or charging current is excessive. Moreover, the sensor detects the remaining charge of the battery and sends indication signal to the controller for displaying for user.
The induced-type power transmission device is commonly used in conventional charger and has constant-voltage/limiting current or constant current/limiting voltage function.
Moreover, the inventive charging device can be applied to those rechargeable battery such as nickel-cadmium (Ni--Cd), Ni-MH or lithium ion battery.